Tata Motors revived the legendary ‘Sierra’ name in November last year. The vehicle has attracted a lot of attention ever since. Interesting design, long list of features, a set of strong engines- it had almost everything that the average Indian buyer seeks in a mid-size SUV. Tata’s new 1.5 Hyperion direct injection turbocharged petrol engine made multiple headlines for its performance and abilities. The carmaker, however, did not reveal its ARAI-certified fuel efficiency figures. Instead, it hypermiled the SUV at NATRAX, resulting in an astonishing mileage of 29.9 kpl. Months passed and Tata seemingly kept mum about the ARAI figures. Now, an RTI response obtained from ARAI has reportedly brought the ARAI mileages of the new Sierra Turbo Petrol And Turbo Diesel trims to light- 13.5 Kmpl for the turbo petrol and 18.8 Kmpl for the turbo diesel! So, what’s going on? Let us take a closer look.
The new Sierra comes with three engine options, including two petrols- 1.5L naturally aspirated petrol (Revotron), 1.5L turbocharged direct injection (TGDi) petrol (Hyperion) and 1.5L turbocharged diesel (Kryojet). The Hyperion was what the carmaker wanted to market the most.
It is a new engine that Tata Motors spent years developing and is said to excel with its performance. Controlled tests on NATRAX showcased the abilities of this engine. Tata Motors, however, did not reveal its ARAI mileage figures, at launch.
India as a market, is sensitive to fuel efficiency. Real-world mileage would be a key factor in defining the market performance of a newly developed turbo-petrol engine. Tata Motors knew this well. The ARAI numbers, as revealed by the RTI response, stand at 13.5kpl- underwhelming for an engine that claims to excel at mileage.
The manufacturer refrained from releasing these numbers. Finally, ‘Vahan Warta’ had to file an RTI petition to obtain the same from ARAI directly. They have shared details of the same on their X (previously Twitter) handle.
The request was filed on 26/11/2025 and was closed on 19/12/2025. Data obtained by Vahan Warta indicates the turbo-petrol and diesel engine to have fuel efficiencies of 13.5kpl and 18.8kpl respectively.
The naturally aspirated petrol engine hasn’t been certified till the date of release of the response. The diesel engine was given its ARAI certification on 21 November while the turbo-petrol got its on 11 December.
Deliveries of the Sierra began in January this year. The SUV has gathered massive interest here. Over 70,000 bookings were recorded within the first 24 hours. The Hyperion engine saw good demand. As days passed, we came across some disappointed Sierra owners on social media, sharing their concerns around the low fuel efficiency of the turbo-petrol engine. This bought fresh questions about the ARAI numbers. We have them now!
The Central Motor Vehicles Rules (CMVR) requires every new car to have its efficiency certified by the Automotive Research Association of India (ARAI) or the International Centre for Automotive Technology (ICAT), as part of homologation before it can be sold in India. Carmakers usually publish ARAI numbers at the time of product launch, to keep things transparent for the buyer. Withholding these is unusual and alarming.
Mid-size SUVs with turbo-petrol engines have relatively higher ARAI mileage figures. The Creta 1.5 TGDi for example, has an ARAI mileage of 18.4 kpl. The Seltos turbo-petrol (DCT) has 17.9 kpl. Even the new Duster 1.3 turbo has an ARAI fuel efficiency of 16.5 kmpl. These are all significantly higher than the Sierra’s numbers.
The ARAI testing occurs under controlled conditions. These numbers are usually higher than real-world mileage. When the ARAI numbers themselves are low, there are high chances that the real-world mileage would be lower.
In simple terms, hypermiling! It is the practice of maximizing fuel efficiency through specialized driving techniques that ensure that the turbocharger works in its most optimal state.
Gentle acceleration, low RPM shifting, and maintaining momentum are all part of these techniques. During the milestone run, the SUV was driven for over 800 km and at a speed of around 70 kph. Clearly, these aren’t practical in real-world driving conditions.